1. Field of Invention
The present invention relates to an organic electroluminescence element (hereinafter sometimes called the “organic EL element” or “EL element”) and the manufacturing method thereof.
Particularly, the present invention relates to an organic EL element which has a large light-emitting area suited for noncommercial and industrial-use display devices (liquid displays and the like) and which can be used for various electrode materials and to the manufacturing method that can obtain such organic EL elements efficiently.
2. Description of Related Art
One example of the conventional organic EL element is disclosed in, for example, JP-A-3-262170. Referring now to FIG. 13, the configuration is explained. An organic layer 202 is interposed between a first electrode 201 and a second electrode 203 and at least the first layer 201 is composed with inorganic semiconductor material, namely, monocrystal semiconductor materials such as GaP, GaAlAs, GaAsP, ZnS, and the like.
When the first electrode 201 is of an n-type semiconductor, the joined surface of the first electrode 201 and the organic layer 202 is made by electron injection joining from the first electrode 201 to the organic layer 202, that is, electron injection is achieved by tunnel effects.
In addition, when the first electrode 201 is of the p-type semiconductor, the joined surface of the first electrode 201 and the organic layer 202 is made by hole injection joining from the first electrode 201 to the organic layer 202, where the hole injection is carried out by the tunnel effects.
Incidentally, in FIG. 13, the first electrode 201 is represented by symbol “P”, the organic layer 202 is represented by symbol “O”, and the second electrode 203 is represented by symbol “M”.
However, the organic EL element disclosed in JP-A-3-262170 has the first electrode 201 which is opposed to the second electrode 203 as shown in FIG. 13, and EL emission light is taken out from either of the electrodes 201 or 203. Consequently, with regard to the light transmittance of the electrode, there are problems in that the electrode material is limited to transparent material, such as indium tin oxide (ITO) or the blue light is difficult to be effectively obtained from the electrodes 201, 203.
Furthermore, the electrodes 201, 203 are composed with monocrystal semiconductor material in these organic EL elements, there is a big restriction in manufacturing. More concretely, since making such monocrystal semiconductor material is not easy, it is difficult to produce an organic EL element with a large area.
Consequently, in JP-A-8-180974 and JP-A-11-31590, or WO97/34447, as shown in FIG. 14, an auxiliary electrode 213 is provided in part of the electrode 212 and the low resistance is obtained as a whole electrode.
However, as electrodes are opposed each other in all inorganic EL electrodes or organic EL elements to transmit the light effectively, consequently, the transparent materials such as ITO must be used for the electrode.
Therefore, the inventors of the present invention diligently have investigated the above-mentioned problems and found out that the conventional problems could be solved by installing an organic light-emitting medium between either an anodic or cathodic electrode (first electrode) and a semiconductor layer comprising non-monocrystal material as well as electrically connecting the other electrode (second electrode) to the edge section of the semiconductor layer.
Accordingly, it is an object of the present invention to provide an organic EL element that can be used for a wide variety of electrode materials and that has a large area, as well as to provide a manufacturing method that can obtain such organic EL element efficiently.